Press release: New gold standard in CAR T-cell therapy with use of Minicircle Sleeping Beauty transposon

Plasmid DNA is used as an active ingredient in vaccines, as a basic substance and raw material in gene and cell therapy, and in viral vector or mRNA production. However, as a result of their manufacture in E. coli cultures, plasmids contain backbone sequences that can trigger immune reactions in target cells. Furthermore, these sequences can result in the undesired proliferation of antibiotic-resistant genes. The research division of PlasmidFactory in Bielefeld has succeeded in synthesising superspiralised DNA, which does not contain any bacterial backbone sequences: Minicircle (MC)-DNA. This means that a new approach is now possible in CAR T-cell therapy.

Non-viral gene transfer using Sleeping Beauty transposition
The Sleeping Beauty (SB) system is based on a transposon that is used in the fields of gene and cell therapy to splice therapeutic sequences into the genome of patients’ cells. By means of chromosomal integration, these sequences become firmly anchored, making it possible to e.g. supplement genetic properties or make the cell identifiable.

Collaboration with Würzburg University Clinic
‘In collaboration with the Würzburg University Clinic, we’ve created a means of performing MC-based SB-transposition of chimeric antigene receptor (CAR) transgenes using this system. This enables us to improve transposition both in comparison to conventional plasmids, and also because the production of CAR T-cells for clinical use is so fast,’ says an enthusiastic Dr Martin Schleef, the Managing Director. The work has just been published in the specialist journal Leukemia (impact factor: 12.1) (Monjezi et al., 2016). ‘This advance makes it possible to synthesise CAR T-cells in a virus-free process based on SB-mediated transposition of MC-DNA, in order to achieve gene transfer in cancer immunotherapy,’ explains Dr Michael Hudecek of the Würzburg University Clinic, pointing out the impressive findings of the joint publication.
Advantages of this approach include a strong safety profile, which results from the nature of the MC itself and the insertion pattern of MC-derived CAR transposons in the T-cell genome.

In the rapidly advancing field of gene and cell therapy, MCs are a preferred vector source for gene transfer because of the high, stable transgene expression they achieve, their secure genomic insertion profile, and the ease with which they can be handled and replicated.

PlasmidFactory possesses exclusive rights to the manufacture of minicircle-based transposon vectors worldwide. Minicircles are derived from parental plasmids, which contain an antibiotic resistance marker, the transposon, and the origin of replication (ori). By means of an intramolecular recombination process, the transposon is excised from this parental plasmid, resulting in a circular, superspiralised (ccc) molecule, the Minicircle.

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